Process for converting limestone into a compressible artificial stone



UNITED STATES PA TENT OFFICE.

CARL LUDR'IG VALEN TIN ZIMMER, OF BERLIN-WILMERSDORF, GERMAEY, ASSIGNbR,BY MESNE ASSIGNMENTS, TO THE CHEMICAL-FOUNDATION, INC., A. CORPORATIONOF DELAWARE.

PROGESS FOR CONVERTING LIMESTONE INTO A COMPR-ESSIBLE AJbTIFICIAL STONE.

Specification of Letters Patent. Patented S t 27 1 21 No Drawing.Original application filed August 11, 1915, Serial No. 45,023. Dividedand this application filed February 7, 1918. Serial No. 215,940.

gust 11, 1915, forLetters Patent of the' United States of America.

Heretofore no process was known for producing an artificial stone whichhas the property of decomposing to a powder when heated, and ofregaining its original hardness under pressure.

Only natural asphaltic limestone, as found at but a few places on theearth in limited quantities, has the specially characteristic propertythat, when heated to 150- 200 (1., it decomposes to a brown, loosepowder which can be compressed by pressure to the hardness of theoriginal stone. Owing to these properties compressed asphalt, made fromasphaltic limestone, is so extensibly used for roads, and the like,since they satisfy all requirements in regard to resistance tomechanical stresses of all kinds, to frost and heat, etc.

Nr at every asphaltic limestone can be used directly for making roads,but only such sorts as contain 812% bitumen, whose melt ing point,moreover, is not hi her than 50 C. (regulation of the road autiorities), If both requirements are not satlsfied, the compressedasphalt will not meet all demands of practice inregard to durability,softening point, etc. Since, even in one and the same mine, the amountof bitumen contained in the stone varies very much, it is extremelydificult to obtain a really good material.

The reason for the great advantages of compressed asphalt made from thenatural product was considered to be due to the intimate mechanicalmixture of the two components: limestone and bitumen. Varidus attemptshave therefore been made to add bitumen to asphaltic limestonecontaining too little bitumen. Heat was also used to assist theoperation, or bitumen was emadditions by Dr. H. Kohler, page 146) havenot result-- analysis and use obtained has only the properties of castasphalt, because according to the processes mentioned the bitumen wasonly brought into mechanical contact with the stone, or, in other words,only surrounds same. Further, all experiments made to mix powderedlimestone or chalk with bitumen or other (compare Chemical Technology edin producing a compressible asphalt, but only a .product having theproperties of cast asphalt, that is, it melts when heated, and it cannotbe compressed, when it solidifies. This nonsuocess was, in the firstplace, due to the fact that the chemical process, which unmistakablytakes place between the bitumen and limestone in nature, was notrecognized. Consequently, an expert came naturally to the conclusionthat the -artificial production of a stone, which, on being heated,decomposes to a loose powder, and can then be compressed, is quiteimpossible.

According to the present invention, it is rendered possible to produce acompressible asphalt synthetically, which not only in shows theproperties of natural asphaltic limestone, but even exceeds same by thefact that not only quantity of bitumen, but also the softening point ofthe bitumen can be chosen within the widest limits, and thus the mostadvantageous composition for any given purpose can be obtained.

In the endeavor to investigate, and, if, possible, to imitate, the oerations which take place in the natural ormation of asphalticlimestone, the inventor first ascertained that the formation of thenatural product cannot have taken place in hot condition, becausenatural asphaltic limestone contains very low boiling hydrocarbons,which are essentially necessary to obtain the desired properties, andcould not be present, if a higher temperature came into question.Further, it was recognized that the formation could not have taken placeby bitumen being simplyv mixed with finely powdered limestone, but thatrather a chemical proc- The second material used, as in nature,is

some bituminous substance, such as natural asphalt, vegetable and animaloils, mineral oils, mineral oil residues, tar, tar oil residues anddistillates.

If such bituminous substances, by means of sulfated sebacic acid, or itsalkaline salts, are converted into an emulsion, this emulsion, in a verydilute condition, will have the property, even at ordinary temperature,to quickly react on the powdered limestone,

and will form an artificial asphaltzic limestone having all theproperties set forth above, the attainment of which forms the object ofthe present application.

The chemical reaction, which takes place between the sebacic acid andthe powdered limestone, causes an intimate union of the limestone andbituminous substances to be efi'ected.

For the purpose in question sulfo-acids of animal and vegetable oil andfats, or their salts, are very suitable. Sulfated ricinoleic acids havebeen found to be of particular advantage. When sucKare used the reactionis finished in a few minutes, and after mixing the materials the vesselmust be quickly emptied, so quickly does the reaction take place. Theproduct obtained is at first an extremely plastic kneadable mass whichdecisively repels water.

The present processis, of course, an invention of the greatestimportance. It is not only suitable to entirely replace natural asphalt,but is even superior to such, inasmuch as this artifical asphalticlimestone, as above mentioned, affords the possibility of choosing ineach case a composition suitable for the particular conditions andtemperature.

The term sebacic acid as used in the claims is intended as a genericterm to include both the acid and its salts, precisely as when onespeaks of a given amount of phosphoric acid in a certain sample of soil.

What I claim and desire to secure by Letters Patent of the United Statesis 1. The herein described process of converting limestone intocompressible artificial stone which consists in mixlng stone containinlime with a bituminous'substance contaming sulfated sebacic acid.

2. The herein described process of converting limestone intocompressible artificial stone which consists in mixing powered limestonewith a bituminous substance in the presence of sulfated sebacic acidcapable of emulsifying the bituminous substance.

CARL LUDWIG VALENTIN ZIMMER.

